Police have arrested two men after a methamphetamine investigation in the upper South Island

Known gang associates were targeted during search warrants issued in Nelson and Marlborough.

Tasman crime manager, Detective Inspector Mark Chenery says police found methamphetamine, a loaded shotgun and ammunition.

A 55-year-old man will appear in the Nelson District Court today on charges including conspiring to deal methamphetamine and unlawful possession of a firearm.

And a 51-year-old man will appear in the Blenheim District Court tomorrow on several drug-related charges.